GardenFacts

All states › Pennsylvania › Harrisburg

Frost dates and planting calendar for Harrisburg, Pennsylvania

Updated October 30, 2026. Based on USDA, NOAA and Colorado State University Extension data. Published by Humblebee.

USDA hardiness zone
7a[1]
Median last spring frost
Apr 15[2]
Median first fall frost
Oct 23[3]
Growing season, median
189 days[4]

Harrisburg is in USDA hardiness zone 7a on the 2023 map[1]. The median last spring frost is April 15, which means half of years see a frost after that date[2].

Frost dates

JanFebMarAprMayJunJulAugSepOctNovDecLast spring frost: 9 in 10 years after Apr 1, half of years Apr 15, 1 in 10 years after May 2Last frostmedian Apr 15First fall frost: 9 in 10 years before Nov 7, half of years Oct 23, 1 in 10 years before Oct 7First frostmedian Oct 23Frost riskHardyHardy vegetables: plant Mar 18 to Apr 1Mar 18 to Apr 1Semi-hardySemi-hardy vegetables: plant Apr 1 to Apr 15Apr 1 to Apr 15TenderTender vegetables: plant around Apr 15around Apr 15Very tenderVery tender vegetables: plant from Apr 29from Apr 29
Shaded: the span between the dates frost passes in 9 of 10 years and 1 of 10 years[2][3]. Green: planting windows from the CSU rules applied to the median last frost (GardenFacts calculation)[6]. Exact dates are in the tables below.

NOAA's 1991 to 2020 records from the Harrisburg 1NE weather station give the frost odds on this page[5]. In 9 of 10 years the last spring frost comes after April 1, and in 1 of 10 years it comes after May 2[2]. In the fall, the first frost comes before October 7 in 1 of 10 years, and before October 23 in half of years[3]. These are chances from past records and not a forecast, so any year can be earlier or later[5].

Frost Likely (9 in 10 years) Even odds (5 in 10) Unlikely (1 in 10)
Last spring frost (32°F)[2] after April 1 after April 15 after May 2
First fall frost (32°F)[3] before October 7 before October 23 before November 7
  • Hard freeze (28°F): median last spring date April 3, median first fall date November 5[7].
  • Frost-free growing season: at least 167 days in 9 of 10 years, 189 days in half of years and 210 days in 1 of 10 years[4].
  • The low reached 32°F or colder in 100% of years and 28°F or colder in 100% of years[8].
  • Weather station: Harrisburg 1NE (USC00363698), 0.9 miles from the city center, 420 feet, 22 years of 1991 to 2020 records[5].

When to plant vegetables

Colorado State University Extension's planting guide was written for Colorado, so these dates are simple arithmetic from its rules[6]. Hardy vegetables such as broccoli, lettuce, peas and spinach can go in as early as 2 to 4 weeks before the median last frost, which is March 18 to April 1[6]. Semi-hardy vegetables such as beets, carrots and potatoes can go in as early as 2 weeks before the median last frost, which is April 1[9]. Tender vegetables such as snap beans and sweet corn can be planted from seed around April 15[10]. Very tender vegetables such as tomatoes and peppers typically start 2 or more weeks after the median last frost, with the earliest start on April 29[11].

  • Hardy (broccoli, cabbage, kohlrabi, lettuce, onions, peas, radishes, spinach, turnips): as early as 2 to 4 weeks before the median last frost (April 15) is March 18 to April 1[6]
  • Semi-hardy (beets, carrots, cauliflower, parsnips, potatoes, Swiss chard): as early as 2 weeks before the median last frost (April 15) is April 1, up to the median date itself[9]
  • Tender (snap beans, sweet corn, cucumbers, summer squash): from seed around the median last frost date, April 15[10]
  • Very tender (cantaloupe, eggplant, peppers, tomatoes, winter squash, watermelon): the earliest start, two weeks after the median last frost (April 15), is April 29[11]
Vegetable (CSU group) Plant from First harvest around
Broccoli (hardy)[12] Mar 18 May 22 (from transplants)
Cabbage (hardy)[12] Mar 18 Jun 11 (from transplants)
Kohlrabi (hardy)[12] Mar 18 May 7
Lettuce (hardy)[12] Mar 18 May 17
Onions (hardy)[12] Mar 18 Jul 6
Peas (hardy)[12] Mar 18 May 22
Radishes (hardy)[12] Mar 18 Apr 17
Spinach (hardy)[12] Mar 18 Apr 27
Turnips (hardy)[12] Mar 18 May 7
Beets (semi-hardy)[12] Apr 1 May 31
Carrots (semi-hardy)[12] Apr 1 Jun 10
Cauliflower (semi-hardy)[12] Apr 1 not listed
Parsnips (semi-hardy)[12] Apr 1 Jun 10
Potatoes (semi-hardy)[12] Apr 1 Aug 4
Swiss chard (semi-hardy)[12] Apr 1 May 31
Snap beans (tender)[12] Apr 15 Jun 14
Sweet corn (tender)[12] Apr 15 Jun 14
Cucumbers (tender)[12] Apr 15 Jun 9
Summer squash (tender)[12] Apr 15 Jun 4
Cantaloupe (very tender)[12] Apr 29 Jul 23
Eggplant (very tender)[12] Apr 29 Jun 28 (from transplants)
Peppers (very tender)[12] Apr 29 Jul 8 (from transplants)
Tomatoes (very tender)[12] Apr 29 Jul 3 (from transplants)
Winter squash (very tender)[12] Apr 29 Aug 7
Watermelon (very tender)[12] Apr 29 Jul 23
Spacing, depth and soil temperature (CSU Extension)
Vegetable Min. soil temp Depth Spacing Days to harvest
Broccoli[13] 40°F 1/2 in 18 in 65
Cabbage[13] 40°F 1/2 in 18 in 85
Kohlrabi[13] 40°F 1/2 in 7-9 in 50
Lettuce[13] 35°F 1/4 in 7-9 in 60
Onions[13] 35°F 1/4 in (seed), 1-2 in (sets) 4-6 in 110
Peas[13] 40°F 1 in 4-6 in 65
Radishes[13] 40°F 1/2 in 2-3 in 30
Spinach[13] 40°F 1/2 in 4-6 in 40
Turnips[13] 40°F 1/2 in 4-6 in 50
Beets[13] 40°F 3/4-1 in 4-6 in 60
Carrots[13] 40°F 1/4 in 2-3 in 70
Cauliflower[13] 40°F 1/2 in 18 in –
Parsnips[13] 35°F 1/2 in 5-6 in 70
Potatoes[13] 45°F – – 125
Swiss chard[13] 40°F 1 in 7-9 in 60
Snap beans[13] 55°F 1-1 1/2 in 6 in 60
Sweet corn[13] 50°F 1-1 1/2 in 12 x 30 in or 9 x 36 in 60-90
Cucumbers[13] 60°F 1 in 6 in trellised, 24-36 in untrellised 55
Summer squash[13] 60°F 1-1 1/2 in 36-48 in 50
Cantaloupe[13] 60°F 1-1 1/2 in 36-48 in 85
Eggplant[13] 60°F 1/4 in 18-24 in 60
Peppers[13] 60°F 1/4 in 15-18 in 70
Tomatoes[13] 50°F 1/4 in 24 in trellised 65
Winter squash[13] 60°F 1-1 1/2 in 36-48 in 100
Watermelon[13] 60°F 1-1 1/2 in 36-48 in 85

Hardiness zone

Zone 7a means the coldest night of the year averages 0°F to 5°F over 1991 to 2020[1]. The zone is based on winter lows, not on summer heat or frost dates[14]. All 7 ZIP code areas that overlap Harrisburg are rated zone 7a[15].

Zone 7a: average annual extreme minimum temperature 0°F to 5°F (1991 to 2020)[1]. Modeled value at the city center: 4.1°F[1].

Share of the city's land area by ZIP code zone: zone 7a 100%[15].

All towns in zone 7a and what zone 7a means

Zone by ZIP code
ZIP code Zone Coldest night range
17110[15] 7a 0 to 5°F
17104[15] 7a 0 to 5°F
17103[15] 7a 0 to 5°F
17102[15] 7a 0 to 5°F
17101[15] 7a 0 to 5°F
17120[15] 7a 0 to 5°F
17111[15] 7a 0 to 5°F

Questions people ask

What growing zone is Harrisburg, PA?
Harrisburg is in USDA zone 7a on the 2023 map[1]. By land area, 100% of the city lies in ZIP code areas rated 7a[15].
When is the last frost in Harrisburg?
The median last spring frost is April 15, so in half of years the last frost comes after that date[2]. In 1 of 10 years it comes after May 2[2].
When is the first frost in Harrisburg?
The median first fall frost is October 23, so in half of years the first frost comes before that date[3]. In 1 of 10 years it comes before October 7[3].
When to plant tomatoes in Harrisburg?
CSU Extension typically starts tomatoes 2 or more weeks after the average last frost, written for Colorado[11]. Using the median last frost, the earliest start is April 29[11].
How long is the growing season in Harrisburg?
The growing season is at least 189 days in half of years[4]. It is at least 167 days in 9 of 10 years[4].

Facts and sources

  1. The 2023 USDA Plant Hardiness Zone Map puts the center of Harrisburg, Pennsylvania in zone 7a. Zone 7a means an average annual extreme minimum temperature of 0°F to 5°F over 1991 to 2020. The map's modeled value at the city center is 4.1°F. USDA zone map 2023 (PRISM, OSU)
  2. Last spring frost (32°F) at this station: in 9 of 10 years the last frost comes after April 1, in half of years after April 15, and in 1 of 10 years after May 2 (NOAA 1991 to 2020 normals). The median last frost date is April 15. NOAA Climate Normals 1991-2020
  3. First fall frost (32°F) at this station: in 1 of 10 years the first frost comes before October 7, in half of years before October 23, and in 9 of 10 years before November 7 (NOAA 1991 to 2020 normals). The median first frost date is October 23. NOAA Climate Normals 1991-2020
  4. Growing season (days between the last spring and first fall 32°F frost) at this station: at least 167 days in 9 of 10 years, at least 189 days in half of years, and at least 210 days in 1 of 10 years. NOAA Climate Normals 1991-2020
  5. Frost dates on this page come from NOAA climate normals for the Harrisburg 1NE weather station (USC00363698), 0.9 miles from the center of Harrisburg at 420 feet, using 22 years of records from 1991 to 2020. NOAA Climate Normals 1991-2020
  6. Colorado State University Extension's vegetable planting guide (written for Colorado) groups broccoli, cabbage, kohlrabi, lettuce, onions, peas, radishes, spinach, turnips as hardy vegetables, with this rule: as early as 2-4 weeks before the average last... CSU Extension GardenNotes #720
  7. Hard freeze (28°F) at this station: the median last spring date is April 3 and the median first fall date is November 5. NOAA Climate Normals 1991-2020
  8. At this station the low reached 32°F or colder in 100% of years from 1991 to 2020, and 28°F or colder in 100% of years. NOAA Climate Normals 1991-2020
  9. Colorado State University Extension's vegetable planting guide (written for Colorado) groups beets, carrots, cauliflower, parsnips, potatoes, Swiss chard as semi-hardy vegetables, with this rule: as early as 0-2 weeks before the average last spring frost.... CSU Extension GardenNotes #720
  10. Colorado State University Extension's vegetable planting guide (written for Colorado) groups snap beans, sweet corn, cucumbers, summer squash as tender vegetables, with this rule: from seed around the average last spring frost; cucumber and summer squash... CSU Extension GardenNotes #720
  11. Colorado State University Extension's vegetable planting guide (written for Colorado) groups cantaloupe, eggplant, peppers, tomatoes, winter squash, watermelon as very tender vegetables, with this rule: typically 2 or more weeks after the average last... CSU Extension GardenNotes #720
  12. GardenFacts calculation: earliest planting date plus CSU days to harvest (table on this page), from the station's median last frost. NOAA Climate Normals 1991-2020
  13. CSU Extension vegetable table: soil temperature, depth, spacing, days to harvest (table on this page). CSU Extension GardenNotes #720
  14. USDA hardiness zones are based on the average annual extreme minimum winter temperature (the coldest night of each winter, averaged over 1991 to 2020 for the 2023 map), not on summer heat or frost dates. Each zone spans 10°F and each half zone (a or b)... USDA Plant Hardiness Zone Map
  15. Harrisburg, Pennsylvania overlaps 7 ZIP code areas. By land area, 100% lies in ZIP code areas rated zone 7a. USDA zone map 2023 (PRISM, OSU)

Frost dates are probabilities from 1991 to 2020 weather records at one NOAA station, not a forecast. Any year can be earlier or later. The hardiness zone describes the average coldest winter night, not frost dates or summer heat. Spots inside the city can differ (ZIP table). Planting rules come from Colorado State University Extension's guide, written for Colorado. A local extension office may give dates tuned to the area. Planting and harvest dates marked GardenFacts calculation are simple arithmetic from the facts above, not advice from the source.

Hardiness zone data: USDA Plant Hardiness Zone Map (2023), USDA Agricultural Research Service and PRISM Group, Oregon State University, prism.oregonstate.edu, accessed October 30, 2026. This is not the official USDA map. Frost data: NOAA NCEI U.S. Climate Normals 1991-2020. Planting rules: Colorado State University Extension.